1. Field of the Invention
This invention relates to a new method for separating the particles from a slurry and dewatering them using air to remove the moisture from between the particles. This new vertical concept prevents the filter cake from becoming the main filtering element and allows the air to reduce the moisture level to previously unachievable levels.
2. Brief Description of Prior Art
Solid-liquid separation is one of the most worked arts in history. Never before has the need for a cost-effective mechanical dewatering process been so great. Our ground water is being destroyed at a frightening rate by the concentrated animal feed operations (CAFO's). CAFO's produce over 375 million tons of manure per year. Large dairy and swine operations are major contributors. The lack of efficient dairy and swine manure management equipment has made The Clean Water Act of 2002 unenforceable. Prior art dewatering systems are not effective because they attempt to press the moisture from the particles and the end result is a compacted mass of wet fiber with little porosity. Others build the cake filtered particles on the filter belt and the filter cake becomes the primary filtering element. The clingosity of the shredded particles tends to grab the smaller undigested gelatinous particles as they pass through the cake reducing the porosity. As the cake builds, the back pressure of the filter cake requires more pressure to move the water through the filter cake. More pressure results in less porosity and blinding is inevitable. Without the ability to move the filtrate through the cake the throughput is limited.
In the past, dairy and swine farmers had no logical choice but to send the nutrient loaded slurry to the manure lagoons.
Not only are we losing our groundwater, an alarming amount of methane, which is 21 more times dangerous than CO2, is being released into our atmosphere. Methane stays in the upper atmosphere trapping heat for 9 to 15 years. We should be capturing the methane for renewable energy and at the same time, reduce the phosphorous poisoning of our groundwater. The electrical energy available in a dairy cow's daily manure will burn a 150 watt light bulb for 24 hours. By using anaerobic digesters to generate biogas to produce energy and by composting the larger fibers as will be described, dairy and swine farmers can turn their expensive manure management problem into something of value.
These things can't be done cost-effectively without an efficient solid-liquid separation (SLS) concept. Every environmentally friendly and efficient dairy and swine manure management flow chart has SLS as one of the required steps.
Several SLS methods and apparatuses have been used to separate and dewater the particles in dairy or swine manure. They generally fall under the categories of centrifuges, hydrocyclones, belt presses, screw presses, diaphragm presses, horizontal filter chambers, rotary disc with vacuum, horizontal belt with vacuum, etc. They all have one or more of the following problems: expensive, unreliable, low throughput, reduced porosity, filter cake blinding, and they fail to meet acceptable moisture levels.
As will be seen from the subsequent description, the preferred embodiments of the present invention overcome the shortcomings of the prior art.